Optimizing pixel settling in an integrated display and capacitive sensing device

ABSTRACT

An example method of performing capacitive sensing and display updating in an integrated capacitive sensing device and display device includes driving a plurality of display electrodes with one or more display voltages from one or more supplies during a first time period, the one or more voltages configured to drive the display pixels. The method further includes initiating a long horizontal blanking interval during a second time period. The method further includes driving a plurality of sensor electrodes with one or more sensing voltages from the one or more supplies during the second time period to perform capacitive sensing. The method further includes activating first circuitry during one of the first time period or the second time period to draw current to equalize power drawn from the one or more supplies during the first and second time periods within a threshold.

BACKGROUND

Field of the Disclosure

Embodiments of disclosure generally relate to integrated display andcapacitive sensing devices and, more particularly, optimizing pixelsettling to minimize display artifacts.

Description of the Related Art

Input devices including proximity sensor devices (also commonly calledtouchpads or touch sensor devices) are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computing systems (such as touch screens integrated in cellularphones).

SUMMARY

Techniques for optimizing pixel settling in an integrated display andcapacitive sensing device are described. In an embodiment, a method ofperforming capacitive sensing and display updating in an integratedcapacitive sensing device and display device includes driving aplurality, of display electrodes with one or more display voltages fromone or more supplies during a first time period, the one or morevoltages configured to drive the display pixels. The method furtherincludes initiating a long horizontal blanking interval during a secondtime period. The method further includes driving a plurality of sensorelectrodes with one or more sensing voltages from the one or moresupplies during the second time period to perform capacitive sensing.The method further includes activating first circuitry during one of thefirst time period or the second time period to draw current to equalizepower drawn from the one or more supplies during the first and secondtime periods within a threshold.

In another embodiment, a processing system for a capacitive sensingdevice and a display device includes source drivers configured to drivea plurality of display electrodes with one or more display voltages fromone or more supplies to drive display pixels of the display deviceduring a first time period. The processing system further includessensing circuitry configured to drive a plurality of sensor electrodeswith one or more sensing voltages from the one or more supplies during asecond time period to perform capacitive sensing. The processing systemfurther includes a controller configured to initiate a long horizontalblanking interval during the second time period. The processing systemfurther includes an equalizer configured to activate first circuitryduring one of the first time period or the second time period to drawcurrent to equalize power drawn from the one or more supplies during thefirst and second time periods within a threshold.

In an embodiment, an input device comprising a capacitive sensing deviceand a display device includes a plurality of display electrodes, aplurality of sensor electrodes, and a processing system coupled to theplurality of display electrodes and the plurality of sensor electrodes.The processing system includes source drivers configured to drive theplurality of display electrodes with one or more voltages from one ormore supplies to drive display pixels of the display device during afirst time period. The processing system further includes sensingcircuitry configured to drive the plurality of sensor electrodes withone or more sensing voltages from the one or more supplies during asecond time period to perform capacitive sensing. The processing systemfurther includes a controller configured to initiate a long horizontalblanking interval during the second time period. The processing systemfurther includes an equalizer configured to activate first circuitryduring one of the first time period or the second time period to drawcurrent to equalize power drawn from the one or more supplies during thefirst and second time periods within a threshold.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a block diagram of an exemplary input device, according to oneembodiment described herein.

FIG. 2 is block diagram depicting a capacitive sensing device of theinput device of FIG. 1 according to some embodiments.

FIG. 3 is an exploded view of a display device according to anembodiment.

FIG. 4 is a block diagram depicting display circuitry of the displaydevice of FIG. 3 according to an embodiment.

FIG. 5 is a block diagram depicting timing of display updating andcapacitive sensing according to an embodiment.

FIG. 6 is a flow diagram depicting a method of performing capacitivesensing and display updated in an integrated capacitive sensing deviceand display device.

FIG. 7 is a flow diagram depicting another method of performingcapacitive sensing and display updated in an integrated capacitivesensing device and display device.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements disclosed in oneembodiment may be beneficially utilized on other embodiments withoutspecific recitation. The drawings referred to here should not beunderstood as being drawn to scale unless specifically noted. Also, thedrawings are often simplified and details or components omitted forclarity of presentation and explanation. The drawings and discussionserve to explain principles discussed below, where like designationsdenote like elements.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of an exemplary input device 100, inaccordance with embodiments of the invention. The input device 100 maybe configured to provide input to an electronic system (not shown). Asused in this document, the term “electronic system” (or “electronicdevice”) broadly refers to any system capable of electronicallyprocessing information. Some non-limiting examples of electronic systemsinclude personal computers of all sizes and shapes, such as desktopcomputers, laptop computers, netbook computers, tablets, web browsers,e-book readers, and personal digital assistants (PDAs). Additionalexample electronic systems include composite input devices, such asphysical keyboards that include input device 100 and separate joysticksor key switches. Further example electronic systems include peripheralssuch as data input devices (including remote controls and mice), anddata output devices (including display screens and printers). Otherexamples include remote terminals, kiosks, and video game machines(e.g., video game consoles, portable gaming devices, and the like).Other examples include communication devices (including cellular phones,such as smart phones), and media devices (including recorders, editors,and players such as televisions, set-top boxes, music players, digitalphoto frames, and digital cameras). Additionally, the electronic systemcould be a host or a slave to the input device.

The input device 100 can be implemented as a physical part of theelectronic system, or can be physically separate from the electronicsystem. As appropriate, the input device 100 may communicate with partsof the electronic system using any one or more of the following: buses,networks, and other wired or wireless interconnections. Examples includeI²C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, and IRDA.

In FIG. 1, the input device 100 is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects 140 in asensing region 120. Example input objects include fingers and styli, asshown in FIG. 1.

Sensing region 120 encompasses any space above, around, in and/or nearthe input device 100 in which the input device 100 is able to detectuser input (e.g., user input provided by one or more input objects 140).The sizes, shapes, and locations of particular sensing regions may varywidely from embodiment to embodiment. In some embodiments, the sensingregion 120 extends from a surface of the input device 100 in one or moredirections into space until signal-to-noise ratios prevent sufficientlyaccurate object detection. The distance to which this sensing region 120extends in a particular direction, in various embodiments, may be on theorder of less than a millimeter, millimeters, centimeters, or more, andmay vary significantly with the type of sensing technology used and theaccuracy desired. Thus, some embodiments sense input that comprises nocontact with any surfaces of the input device 100, contact with an inputsurface (e.g. a touch surface) of the input device 100, contact with aninput surface of the input device 100 coupled with some amount ofapplied force or pressure, and/or a combination thereof. In variousembodiments, input surfaces may be provided by surfaces of casingswithin which the sensor electrodes reside, by face sheets applied overthe sensor electrodes or any casings, etc. In some embodiments, thesensing region 120 has a rectangular shape when projected onto an inputsurface of the input device 100.

The input device 100 may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region 120.The input device 100 comprises one or more sensing elements fordetecting user input. As several non-limiting examples, the input device100 may use capacitive, elastive, resistive, inductive, magnetic,acoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes.

In some capacitive implementations of the input device 100, voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g. system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects.

Some capacitive implementations utilize “mutual capacitance” (or“transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a transcapacitive sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitters”) and one ormore receiver sensor electrodes (also “receiver electrodes” or“receivers”). Transmitter sensor electrodes may be modulated relative toa reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. A resulting signal may comprise effect(s) corresponding to oneor more transmitter signals, and/or to one or more sources ofenvironmental interference (e.g. other electromagnetic signals). Sensorelectrodes may be dedicated transmitters or receivers, or may beconfigured to both transmit and receive.

In FIG. 1, a processing system 110 is shown as part of the input device100. The processing system 110 is configured to operate the hardware ofthe input device 100 to detect input in the sensing region 120. Theprocessing system 110 comprises parts of or all of one or moreintegrated circuits (ICs) and/or other circuitry components. Forexample, a processing system for a mutual capacitance sensor device maycomprise transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes). In some embodiments,the processing system 110 also comprises electronically-readableinstructions, such as firmware code, software code, and/or the like. Insome embodiments, components composing the processing system 110 arelocated together, such as near sensing element(s) of the input device100. In other embodiments, components of processing system 110 arephysically separate with one or more components close to sensingelement(s) of input device 100, and one or more components elsewhere.For example, the input device 100 may be a peripheral coupled to adesktop computer, and the processing system 110 may comprise softwareconfigured to run on a central processing unit of the desktop computerand one or more ICs (perhaps with associated firmware) separate from thecentral processing unit. As another example, the input device 100 may bephysically integrated in a phone, and the processing system 110 maycomprise circuits and firmware that are part of a main processor of thephone. In some embodiments, the processing system 110 is dedicated toimplementing the input device 100. In other embodiments, the processingsystem 110 also performs other functions, such as operating displayscreens, driving haptic actuators, etc.

The processing system 110 may be implemented as a set of modules thathandle different functions of the processing system 110. Each module maycomprise circuitry that is a part of the processing system 110,firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. Example modules includehardware operation modules for operating hardware such as sensorelectrodes and display screens, data processing modules for processingdata such as sensor signals and positional information, and reportingmodules for reporting information. Further example modules includesensor operation modules configured to operate sensing element(s) todetect input, identification modules configured to identify gesturessuch as mode changing gestures, and mode changing modules for changingoperation modes.

In some embodiments, the processing system 110 responds to user input(or lack of user input) in the sensing region 120 directly by causingone or more actions. Example actions include changing operation modes,as well as GUI actions such as cursor movement, selection, menunavigation, and other functions. In some embodiments, the processingsystem 110 provides information about the input (or lack of input) tosome part of the electronic system (e.g. to a central processing systemof the electronic system that is separate from the processing system110, if such a separate central processing system exists). In someembodiments, some part of the electronic system processes informationreceived from the processing system 110 to act on user input, such as tofacilitate a full range of actions, including mode changing actions andGUI actions.

For example, in some embodiments, the processing system 110 operates thesensing element(s) of the input device 100 to produce electrical signalsindicative of input (or lack of input) in the sensing region 120. Theprocessing system 110 may perform any appropriate amount of processingon the electrical signals in producing the information provided to theelectronic system. For example, the processing system 110 may digitizeanalog electrical signals obtained from the sensor electrodes. Asanother example, the processing system 110 may perform filtering orother signal conditioning. As yet another example, the processing system110 may subtract or otherwise account for a baseline, such that theinformation reflects a difference between the electrical signals and thebaseline. As yet further examples, the processing system 110 maydetermine positional information, recognize inputs as commands,recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device 100 is implemented with additionalinput components that are operated by the processing system 110 or bysome other processing system. These additional input components mayprovide redundant functionality for input in the sensing region 120, orsome other functionality. FIG. 1 shows buttons 130 near the sensingregion 120 that can be used to facilitate selection of items using theinput device 100. Other types of additional input components includesliders, balls, wheels, switches, and the like. Conversely, in someembodiments, the input device 100 may be implemented with no other inputcomponents.

In some embodiments, the input device 100 comprises a touch screeninterface, and the sensing region 120 overlaps at least part of anactive area of a display screen. For example, the input device 100 maycomprise substantially transparent sensor electrodes overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system. The display screen may be any type of dynamic displaycapable of displaying a visual interface to a user, and may include anytype of light emitting diode (LED), organic LED (OLED), cathode ray tube(CRT), liquid crystal display (LCD), plasma, electroluminescence (EL),or other display technology. The input device 100 and the display screenmay share physical elements. For example, some embodiments may utilizesome of the same electrical components for displaying and sensing. Asanother example, the display screen may be operated in part or in totalby the processing system 110.

It should be understood that while many embodiments of the invention aredescribed in the context of a fully functioning apparatus, themechanisms of the present invention are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present invention may be implemented anddistributed as a software program on information bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediareadable by the processing system 110). Additionally, the embodiments ofthe present invention apply equally regardless of the particular type ofmedium used to carry out the distribution. Examples of non-transitory,electronically readable media include various discs, memory sticks,memory cards, memory modules, and the like. Electronically readablemedia may be based on flash, optical, magnetic, holographic, or anyother storage technology.

FIG. 2 is a block diagram depicting a capacitive sensing device 200 ofthe input device 100 according to some embodiments. For clarity ofillustration and description, FIG. 2 shows the sensing elements of thecapacitive sensing device 200 in a pattern of simple rectangles and doesnot show various components, such as various interconnects between thesensing elements and the processing system 110. An electrode pattern 250comprises a first plurality of sensor electrodes 260 (260-1, 260-2,260-3, . . . 260-n), and a second plurality of sensor electrodes 270(270-1, 270-2, 270-3, . . . 270-m) disposed over the first plurality ofelectrodes 260. In the example shown, n=m=4, but in general n and m areeach positive integers and not necessarily equal to each other. Invarious embodiments, the first plurality of sensor electrodes 260 areoperated as a plurality of transmitter electrodes (referred tospecifically as “transmitter electrodes 260”), and the second pluralityof sensor electrodes 270 are operated as a plurality of receiverelectrodes (referred to specifically as “receiver electrodes 270”). Inanother embodiment, one plurality of sensor electrodes may be configuredto transmit and receive and the other plurality of sensor electrodes mayalso be configured to transmit and receive. Further processing system110 can receive resulting signals with one or more sensor electrodes ofthe first and/or second plurality of sensor electrodes while the one ormore sensor electrodes are modulated with absolute capacitive sensingsignals. The first plurality of sensor electrodes 260, the secondplurality of sensor electrodes 270, or both can be disposed within thesensing region 120. The electrode pattern 250 is coupled to theprocessing system 110 through routing traces (discussed below).

The first plurality of electrodes 260 and the second plurality ofelectrodes 270 are typically ohmically isolated from each other. Thatis, one or more insulators separate the first plurality of electrodes260 and the second plurality of electrodes 270 and prevent them fromelectrically shorting to each other. In some embodiments, the firstplurality of electrodes 260 and the second plurality of electrodes 270are separated by insulative material disposed between them at cross-overareas; in such constructions, the first plurality of electrodes 260and/or the second plurality of electrodes 270 can be formed with jumpersconnecting different portions of the same electrode. In someembodiments, the first plurality of electrodes 260 and the secondplurality of electrodes 270 are separated by one or more layers ofinsulative material. In such embodiments, the first plurality ofelectrodes 260 and the second plurality of electrodes 270 can bedisposed on separate layers of a common substrate. In some otherembodiments, the first plurality of electrodes 260 and the secondplurality of electrodes 270 are separated by one or more substrates; forexample, the first plurality of electrodes 260 and the second pluralityof electrodes 270 can be disposed on opposite sides of the samesubstrate, or on different substrates that are laminated together. Insome embodiments, the first plurality of electrodes 260 and the secondplurality of electrodes 270 can be disposed on the same side of a singlesubstrate.

The areas of localized capacitive coupling between the first pluralityof sensor electrodes 260 and the second plurality sensor electrodes 270may be form “capacitive pixels” of a “capacitive image.” The capacitivecoupling between sensor electrodes of the first and second pluralities260 and 270 changes with the proximity and motion of input objects inthe sensing region 120. Further, in various embodiments, the localizedcapacitive coupling between each of the first plurality of sensorelectrodes 260 and the second plurality of sensor electrodes 270 and aninput object may be termed “capacitive pixels” of a “capacitive image.”In some embodiments, the localized capacitive coupling between each ofthe first plurality of sensor electrodes 260 and the second plurality ofsensor electrodes 270 and an input object may be termed “capacitivemeasurements” of “capacitive profiles.”

The processing system 110 can include a front end 208 having sensorcircuitry 204. The sensor circuitry 204 operates the electrode pattern250 to receive resulting signals from sensor electrodes using acapacitive sensing signal having a sensing frequency. The processingsystem 110 can include a processing module 220 configured to determinecapacitive measurements from the resulting signals. The processingmodule 220 can include processor circuitry 226, such as a digital signalprocessor (DSP), microprocessor, or the like. The processing module 220can include memory 228 configured to store software and/or firmwareconfigured for execution by processor circuitry 226 to implement variousfunctions, such as determining object position from the resultingsignals. Alternatively, some or all of the functions of the processormodule 220 can be implemented entirely in hardware (e.g., usingintegrated circuitry). The processing module 220 can track changes incapacitive measurements to detect input object(s) in the sensing region120. The processing system 110 can include other modular configurations,and the functions performed by the front end 208 and the processingmodule 220 can, in general, be performed by one or more modules orcircuits in the processing system 110. The processing system 110 caninclude other modules and circuits, and can perform other functions asdescribed in some embodiments below.

The processing system 110 can operate in absolute capacitive sensingmode or transcapacitive sensing mode. In absolute capacitive sensingmode, receiver(s) in the sensor circuitry 204 measure voltage, current,or charge on sensor electrode(s) in the electrode pattern 250 while thesensor electrode(s) are modulated with absolute capacitive sensingsignals to generate the resulting signals. The processing module 220generates absolute capacitive measurements from the resulting signals.The processing module 220 can track changes in absolute capacitivemeasurements to detect input object(s) in the sensing region 120.

In transcapacitive sensing mode, transmitter(s) in the sensor circuitry204 drive one or more of the first plurality of electrodes 260 with thecapacitive sensing signal (also referred to as a transmitter signal ormodulated signal in the transcapacitive sensing mode). Receiver(s) inthe sensor circuitry 204 measure voltage, current, or charge on one ormore of the second plurality of electrodes 270 to generate the resultingsignals. The resulting signals comprise the effects of the capacitivesensing signal and input object(s) in the sensing region 120. Theprocessing module 220 generates transcapacitive measurements from theresulting signals. The processing module 220 can track changes intranscapacitive measurements to detect input object(s) in the sensingregion 120.

In some embodiments, the processing system 110 “scans” the electrodepattern 250 to determine capacitive measurements. In the transcapacitivesensing mode, the processing system 110 can drive the first plurality ofelectrodes 260 to transmit transmitter signal(s). The processing system110 can operate the first plurality of electrodes 260 such that onetransmitter electrode transmits at one time, or multiple transmitterelectrodes transmit at the same time. Where multiple transmitterelectrodes transmit simultaneously, these multiple transmitterelectrodes may transmit the same transmitter signal and effectivelyproduce a larger transmitter electrode, or these multiple transmitterelectrodes may transmit different transmitter signals. For example,multiple transmitter electrodes may transmit different transmittersignals according to one or more coding schemes that enable theircombined effects on the resulting signals of the second plurality ofelectrodes 270 to be independently determined. In the absolutecapacitive sensing mode, the processing system 110 can receivingresulting signals from one sensor electrode 260, 270 at a time, or froma plurality of sensor electrodes 260, 270 at a time. In either mode, theprocessing system 110 can operate the second plurality of electrodes 270singly or collectively to acquire resulting signals. In absolutecapacitive sensing mode, the processing system 110 can concurrentlydrive all electrodes along one or more axes. In some examples, theprocessing system 110 can drive electrodes along one axis (e.g., alongthe first plurality of sensor electrodes 260) while electrodes alonganother axis are driven with a shield signal, guard signal, or the like.In some examples, some electrodes along one axis and some electrodesalong the other axis can be driven concurrently.

In the transcapacitive sensing mode, the processing system 110 can usethe resulting signals to determine capacitive measurements at thecapacitive pixels. A set of measurements from the capacitive pixels forma “capacitive image” (also “capacitive frame”) representative of thecapacitive measurements at the pixels. The processing system 110 canacquire multiple capacitive images over multiple time periods, and candetermine differences between capacitive images to derive informationabout input in the sensing region 120. For example, the processingsystem 110 can use successive capacitive images acquired over successiveperiods of time to track the motion(s) of one or more input objectsentering, exiting, and within the sensing region 120.

In absolute capacitive sensing mode, the processing system 110 can usethe resulting signals to determine capacitive measurements along an axisof the sensor electrodes 260 and/or an axis of the sensor electrodes270. A set of such measurements forms a “capacitive profile”representative of the capacitive measurements along the axis. Theprocessing system 110 can acquire multiple capacitive profiles along oneor both of the axes over multiple time periods and can determinedifferences between capacitive profiles to derive information aboutinput in the sensing region 120. For example, the processing system 110can use successive capacitive profiles acquired over successive periodsof time to track location or proximity of input objects within thesensing region 120. In other embodiments, each sensor can be acapacitive pixel of a capacitive image and the absolute capacitivesensing mode can be used to generate capacitive image(s) in addition toor in place of capacitive profiles.

The baseline capacitance of the input device 100 is the capacitive imageor capacitive profile associated with no input object in the sensingregion 120. The baseline capacitance changes with the environment andoperating conditions, and the processing system 110 can estimate thebaseline capacitance in various ways. For example, in some embodiments,the processing system 110 takes “baseline images” or “baseline profiles”when no input object is determined to be in the sensing region 120, anduses those baseline images or baseline profiles as estimates of baselinecapacitances. The processing module 220 can account for the baselinecapacitance in the capacitive measurements and thus the capacitivemeasurements can be referred to as “delta capacitive measurements”.Thus, the term “capacitive measurements” as used herein encompassesdelta-measurements with respect to a determined baseline.

In some touch screen embodiments, at least one of the first plurality ofsensor electrodes 260 and the second plurality of sensor electrodes 270comprise one or more display electrodes of a display device 280 used inupdating a display of a display screen, such as one or more segments ofa “Vcom” electrode (common electrodes), gate electrodes, sourceelectrodes, anode electrode and/or cathode electrode. These displayelectrodes may be disposed on an appropriate display screen substrate.For example, the display electrodes may be disposed on a transparentsubstrate (a glass substrate, TFT glass, or any other transparentmaterial) in some display screens (e.g., In Plane Switching (IPS) orPlane to Line Switching (PLS) Organic Light Emitting Diode (OLED)), onthe bottom of the color filter glass of some display screens (e.g.,Patterned Vertical Alignment (PVA) or Multi-domain Vertical Alignment(MVA)), over an emissive layer (OLED), etc. The display electrodes canalso be referred to as “common electrodes,” since the display electrodesperform functions of display updating and capacitive sensing. In variousembodiments, each sensor electrode of the first and/or second pluralityof sensor electrodes 260 and 270 comprises one or more commonelectrodes. In other embodiments, at least two sensor electrodes of thefirst plurality of sensor electrodes 260 or at least two sensorelectrodes of the second plurality of sensor electrodes 270 may share atleast one common electrode. Furthermore, in one embodiment, both thefirst plurality of sensor electrodes 260 and the second pluralityelectrodes 270 are disposed within a display stack on the display screensubstrate. An example display stack is described below with respect toFIG. 3. Additionally, at least one of the sensor electrodes 260, 270 inthe display stack may comprise a common electrode. However, in otherembodiments, only the first plurality of sensor electrodes 260 or thesecond plurality of sensor electrodes 270 (but not both) are disposedwithin the display stack, while other sensor electrodes are outside ofthe display stack (e.g., disposed on an opposite side of a color filterglass).

In an embodiment, the processing system 110 comprises a singleintegrated controller, such as an application specific integratedcircuit (ASIC), having the front end 208, the processing module 220, andany other module(s) and/or circuit(s). In another embodiment, theprocessing system 110 can include a plurality of integrated circuits,where the front end 208, the processing module 220, and any othermodule(s) and/or circuit(s) can be divided among the integratedcircuits. For example, the front end 208 can be on one integratedcircuit, and the processing module 220 and any other module(s)and/circuit(s) can be one or more other integrated circuits. In someembodiments, a first portion of the front end 208 can be on oneintegrated circuit and a second portion of the front end 208 can be onsecond integrated circuit. In such embodiments, at least one of thefirst and second integrated circuits comprises at least portions ofother modules, such as a display driver module and/or a display drivermodule.

The processing system 110 is coupled to a power management IC 222. Thepower management IC 222 includes one or more power supplies 224. Each ofthe power supplies 224 provides a particular voltage for use by theprocessing system 110. For example, the power supplies 224 can outputone or more display voltages for use by the display driver circuitry 210(discussed below). The power supplies can output one or more sensingvoltages for use by the sensor circuitry 204. The power supplies 224 cangenerate the supply voltages from an input power source (e.g., abattery) (not shown). For example, the power supplies 224 can includeone or more DC-to-DC converters for outputting the various supplyvoltages of different DC voltage levels given one or more input DCvoltages.

FIG. 3 is an exploded view of the display device 280 according to anembodiment. The capacitive sensing device 200 is integrated with thedisplay device 280. The display device 280 generally includes aplurality of transparent substrates positioned over a first substrate,referred to herein as thin-film transistor (TFT) glass 302. An activeelement 304 is formed on the TFT glass 302. The active element 304includes TFT layers 322 that form display update circuitry configured toupdate a plurality of pixels. The TFT layers 322 of the active element304 can be electrically coupled to display electrodes, including pixelelectrodes 322 and Vcom electrodes 306. In an embodiment, the Vcomelectrodes 306 are disposed on the TFT glass 302. In the embodimentshown, the Vcom electrodes 306 are disposed on the top TFT layers 322 ofthe active element 304. In some embodiments, the Vcom electrodes 306 aresegmented into a plurality of common electrodes and used for bothdisplay updating and capacitive sensing. The Vcom electrodes 306 canalso include electrodes that are used only for display updating. Inother embodiments, the Vcom electrodes 306 can be located in a differentlayer, such as under the color filter glass 312 (described below).

The display device 280 includes a second substrate, referred to hereinas color filter glass 312, a lens 318, an optional polarizer 316, and anoptional anti-shatter film 314. A layer of display material 308 (e.g.,liquid crystal) is disposed between the color filter glass 312 and theTFT glass 302. In an embodiment, layer(s) 310 between the color filterglass 312 and the display material 308 include one or more color filtersand a black mask. A region between and including the color filter glass312 and the TFT glass 302 is referred to herein as display stack 350.

In one embodiment, sensing elements of the capacitive sensing device 200are disposed at least partially within the display stack 350. Sensingelements, such as receiver electrodes 270, can be disposed between thecolor filter glass 312 and the display material 322 (e.g., withinlayer(s) 310). Sensing elements, such as transmitter electrodes 260, canbe common electrodes of the Vcom electrodes 306. In other embodiments,receiver electrodes 270 can be disposed outside of the display stack280, such as on the color filter glass 312 outside of the display stack280.

FIG. 4 is a block diagram depicting display circuitry 450 of the displaydevice 280 according to an embodiment. The display circuitry 450 can beformed in the active element 304 of the display stack 350. The displaycircuitry 450 is coupled to source drivers 212 through switches 410. Thedisplay circuitry 450 is also coupled to gate selection circuitry 214.For purposes of clarity, the display electrodes are omitted from FIG. 4.

The source drivers 212 are coupled to source lines 408 of the displaycircuitry 450 through the switches 410. The switches 410 selectivelycouple individual source drivers 212 to the source lines 408. The gateselection circuitry 214 is coupled to gate lines 406 of the displaycircuitry 450. The display circuitry 450 includes a plurality of pixels404, each of which is coupled to one or more TFTs 402. A source of eachTFT 402 is coupled to a respective source line. A gate of each TFT 402is coupled to a respective gate line. A drain of each TFT 402 is coupledto a pixel electrode of a respective pixel 404. Each source line 408drives TFTs in a column of pixels 404. Each gate line 406 drives TFTs ina row of pixels 404. The pixels 404 are used to display an image on adisplay screen. By coordinating the gate voltages provided by the gateselection circuitry 214 and the source voltages provided by the sourcedrivers 212, the display driver circuitry 210 can set the pixels 404 anddisplay an image on a display screen.

Returning to FIG. 2, in an embodiment, the source drivers 212 are partof display diver circuitry 210 in the front end 208 of the processingsystem 110. That is, the front end 208 of the processing system 110 canbe configured to perform both display updating and capacitive sensing.In an embodiment, the display driver circuitry 210 can also include thegate selection circuitry 214. In other embodiments, the gate selectioncircuitry 214 can be located external to the processing system 110, suchas in another integrated circuit. In an embodiment, the gate selectioncircuitry 214 is disposed in the display circuitry 450 (e.g., agate-in-panel (GIP) type of display device).

The front end 208 also includes a controller 232. The controller 232 isconfigured to alternately control the sensor circuitry 204 to performcapacitive sensing and the display driver circuitry 210 to performdisplay updating. FIG. 5 is a block diagram depicting timing of displayupdating and capacitive sensing according to an embodiment. Thecontroller 232 can control the display driver circuitry 210 to updatethe display during a display update period 502. The terms “period” and“interval” are used interchangeably herein. The controller 232 cancontrol the sensor circuitry 204 to perform capacitive sensing during along horizontal blanking period 506 (also referred to as the longH-blank interval or long H-blank period). The long H-blank period 506 isas long as or longer than the conventional horizontal blanking intervalof the display (referred to as Hblank). In an embodiment, the controller232 can control the display driver circuitry 210 to update one or morelines during each display update period 502. The controller 232 can alsoimplement a vertical blanking interval (not shown) after all lines havebeen updated.

Returning to FIG. 2, a display such as an LCD display is typicallydesigned assuming that all lines are rendered in a contiguous mannerbetween vertical blanking intervals. As discussed above, however, thecontroller 232 implements a long H-blank interval 506 in order toperform capacitive sensing. Increasing the duration of the long H-blankinterval 506 from the duration of the conventional Hblank interval canresult in display artifacts for various reasons. Notably, the longH-blank interval can cause transient variations in supply voltage,transient variations in Vcom voltage level, variation in pixel settling,variation in gate voltage levels, or a combination thereof. Some or allof these effects can lead to display artifacts. In an embodiment, theprocessing system 110 is configured to mitigate such display artifactsthat result from the long H-blank interval 506.

In an embodiment, the processing system 110 includes a power equalizer(“equalizer 230”). In an embodiment, the equalizer 230 is implemented asfirmware (“equalizer firmware 230A”) executed by the processor 226 inthe processing module 220. In another embodiment, the equalizer 230 isimplemented as an equalizer circuit 230B. In yet another embodiment, theequalizer 230 is implemented as a combination of the equalizer firmware230A and the equalizer circuit 230B. In general, the equalizer 230 isconfigured to activate first circuitry during one of a first time periodor second time period to draw current to equalize power drawn from thepower supplies 224 during the first and second time periods. In anembodiment, the first time period corresponds to the display updateperiod 502 and the second time period corresponds to the long H-blankinterval 506.

During the display update period 502, the display driver circuitry 210operates using supply voltage(s) from power supplies 224 and draws acurrent, referred to as I_(display). During the long H-blank interval506, the sensor circuitry 204 operates using supply voltage(s) from thepower supplies 224 and draws a current, referred to as I_(sense).Typically, the sensor circuitry 204 operates at lower voltage(s) thanthe display driver circuitry 210 and thus the current I_(sense) is lessthan the current I_(display). The response of the power supplies 224 isnot instantaneous. As such, without equalization, transients can begenerated when the display driver circuitry 210 attempts to drawI_(display) after the power supplies 224 have been supplying I_(sense)to the sensor circuitry 204. The power supplies 224 cannot immediatelyoutput I_(display) at the start of the display update period 502. Assuch, without equalization, some pixel(s) in the display will benoticeably dimmer than other pixels. The equalizer 230 operates toreduce the difference between I_(display) and I_(sense), which in turnreduces the transients and mitigates the display artifacts.

In an embodiment, the equalizer 230 implements power equalization bycausing the consumption of additional current during the long H-blankinterval 506. For example, the equalizer 230 can activate one or more ofthe source drivers 212 during the long H-blank interval 506. Theequalizer 230 can control the source drivers 212 through an activateinput 412. During the long H-blank interval 506, the switches 410disconnect the source drivers 212 from the source lines 408. As such,the equalizer 230 can activate one or more of the source drivers 212 forthe purpose of consuming additional current without affecting thepixels. The equalizer 230 can activate one or more source drivers 212 toconsume a current I_(additional). As such, the current drawn from thepower supplies 224 during the long H-blank interval 506 isI_(sense)+I_(additional), which reduces the difference between thecurrent drawn during the display update period 502 and the current drawnduring the long H-blank interval 506. The equalizer 230 can equalize thepower drawn from the power supplies 224 to within a given threshold bycontrolling the current I_(additional).

In another embodiment, the processing system 110 can include dedicatedcurrent consumption circuits 234. Rather than activating the sourcedrivers 212, the equalizer 230 can activate one or more of the currentconsumption circuits 234 during the long H-blank interval 506 to drawthe current I_(additional). In yet another embodiment, the equalizer 230can activate both one or more source drivers 212 and one or more currentconsumption circuits 234 during the long H-blank interval 506 to drawthe current I_(additional).

In an embodiment, the equalizer 230 implements power equalization bycausing the reduction of current during the display update period 502.That is, the equalizer 230 operates to reduce the current I_(display).For example, the equalizer 230 can control the source drivers 212through a drive setting input 414 to reduce the operating voltage of thesource drivers 212. The reduction in operating voltage results in areduction in the current I_(display) drawn from the power supplies 224.The reduction in operating voltage also results in dimmer pixels of thedisplay. However, since all pixels would be dimmed uniformly, thereduction in operating voltage would not cause noticeable displayartifacts. Further, the dimming of pixels due to lower operating voltagecan be compensated by increasing the output of the backlight. In anembodiment, the equalizer 230 controls the source drivers 212 during thedisplay update period 502 to draw a current I_(display)−I_(reduction),which reduces the difference between the current drawn during thedisplay update period 502 and the current drawn during the long H-blankinterval 506. The equalizer 230 can equalize the power drawn from thepower supplies 224 to within a given threshold by controlling thecurrent I_(display)−I_(reduction).

In an embodiment, the equalizer 230 can implement power equalization byboth causing a reduction of current drawn during the display updateperiod 502 and the increase in current drawn during the long H-blankperiod 506. That is, the equalizer 230 can control the source drivers212 to draw a current I_(display)−I_(reduction) from the power supplies224 during the display update period 502. In addition, the equalizer 230can control source driver(s) 212 and/or current consumption circuit(s)234 to draw a current I_(additional) from the power supplies 224 duringthe long H-blank interval 506. The equalizer 230 can equalize the powerdrawn from the power supplies 224 to within a given threshold bycontrolling the current I_(additional) and the currentI_(display)−I_(reduction).

In the examples described above, the current drawn from the powersupplies 224 during the display update period 502 (first time period) isassumed to be larger than the current drawn from the power supplies 224during the long H-blank interval 506 (second time period). In otherembodiments, the equalizer 230 can operate given the converseconfiguration. That is, in other embodiments, the current drawn from thepower supplies 224 during the display update period 502 (first timeperiod) can be smaller than the current drawn from the power supplies224 during the long H-blank interval 506. In such case, the equalizer230 can activate one or more current consumption circuits 234 and/or oneor more source drivers 212 during the display update period 502 toconsume a current I_(additional) during the display update period 502.Alternatively or additionally, the equalizer 230 can reduce the currentdrawn by the sensor circuitry 204 by a current I_(reduction) during thelong H-blank interval 506.

FIG. 6 is a flow diagram depicting a method 600 of performing capacitivesensing and display updated in an integrated capacitive sensing deviceand display device. The method 600 can be performed by the processingsystem 110. Various steps of the method 600 can be performed by thecomponents of the processing system 110 described above. In the method600, it is assumed that the current drawn during the display updateperiod 502 is greater than the current drawn during the long H-blankperiod 506.

The method 600 begins at step 602, where the display driver circuitry210 drives the display electrodes with display voltage(s) from the powersupplies 224 during a first time period to perform display updating.That is, the first time period is the display update period 502. A step604, the controller 232 initiates a long horizontal blanking intervalduring a second time period. That is, the second time period is the longH-blank interval 506. At step 606, the sensor circuitry 204 drives thesensor electrodes with sensing voltage(s) from the power supplies 224during the second time period to perform capacitive sensing. Thecontroller 232 can control the operation of the display driver circuitry210 and the sensor circuitry 204 during steps 602 and 606 to implementthe timing of the display update period 502 and the long H-blankinterval 506 described above with respect to FIG. 5.

During step 606, at step 608, the equalizer 230 activates firstcircuitry during the second time period to draw current to equalizepower drawn from the power supplies 224 during the first and second timeperiods within a threshold. In an embodiment, the first circuitrycomprises one or more of the source drivers 212. Thus, at step 610, theequalizer 230 can drive source driver(s) 212 during the second timeperiod while the source drivers are disconnected from the display.Alternatively, at step 612, the equalizer 230 can activate one or moreof the current consumption circuit(s) 234 during the second time period.In another embodiment, the equalizer can perform both steps 610 and step612. In an embodiment, the equalizer 230 performs step 608 during thesecond time period (e.g., the long H-blank interval 506).

In an embodiment, the equalizer 230 can perform the following algorithmduring step 608: (1) the equalizer 230 can determine a thresholdrepresenting a target difference between the current drawn during thedisplay update period 502 and the current drawn during the long H-blankinterval 506; (2) the equalizer 230 can determine a currentI_(additional) that makes the difference between the current drawnduring the display update period 502 and (I_(sense)+I_(additional)) lessthan or equal to the threshold; (3) the equalizer 230 can determine thenumber of source drivers 212 and/or the number of current consumptioncircuits 234 to be activated that consume I_(additional); and (4) theequalizer 230 can activate the selected source drivers 212 and/orcurrent consumption circuits 234 to consume the current I_(additional).

During the step 602, at step 614, the equalizer 230 can control secondcircuitry during the first time period to equalize power drawn from thepower supplies 224 during the first and second time periods within athreshold. In an embodiment, the second circuitry comprises the sourcedrivers 212. Thus, at step 616, the equalizer 230 can reduce the currentconsumed by the source driver(s) 212 during the first time period whilethe source drivers 212 are connected to the display.

In an embodiment, the equalizer 230 can perform the following algorithmduring step 614: (1) the equalizer 230 can determine a thresholdrepresenting a target difference between the current drawn during thedisplay update period 502 and the current and the current drawn duringthe long H-blank interval 506; (2) the equalizer 230 can determine acurrent I_(reduction) that makes the difference between the currentdrawn during the display update period 502 and the current drawn duringthe long H-blank period 506 less than or equal to the threshold; (3) theequalizer 230 can determine an operating voltage for the source drivers212 to consume (I_(display)−I_(reduction)); and (4) the equalizer 230can control the drive setting of the source drivers 212 consume thecurrent (I_(display)−I_(reduction)).

In an embodiment, the equalizer 230 can perform a combination of steps616 and steps 610 and/or 612.

FIG. 7 is a flow diagram depicting a method 700 of performing capacitivesensing and display updated in an integrated capacitive sensing deviceand display device. The method 700 can be performed by the processingsystem 110. Various steps of the method 700 can be performed by thecomponents of the processing system 110 described above. In the method700, it is assumed that the current drawn during the long H-blank period506 is greater than the current drawn during the display update period502. Elements of FIG. 7 that are the same or similar to those of FIG. 6are designated with identical reference numerals and are describedabove.

During step 602, at step 708, the equalizer 230 activates firstcircuitry during the first time period to draw current to equalize powerdrawn from the power supplies 224 during the first and second timeperiods within a threshold. In an embodiment, the first circuitrycomprises one or more of the source drivers 212 not connected to thedisplay by the switches 410. Thus, at step 710, the equalizer 230 candrive source driver(s) 212 during the first time period while thosesource drivers are disconnected from the display. Alternatively, at step712, the equalizer 230 can activate one or more of the currentconsumption circuit(s) 234 during the first time period. In anotherembodiment, the equalizer can perform both steps 710 and step 712. In anembodiment, the equalizer 230 performs step 608 during the second timeperiod (e.g., the long H-blank interval 506).

In an embodiment, the equalizer 230 can perform the following algorithmduring step 708: (1) the equalizer 230 can determine a thresholdrepresenting a target difference between the current drawn during thedisplay update period 502 and the current drawn during the long H-blankinterval 506; (2) the equalizer 230 can determine a currentI_(additional) that makes the difference between the current drawnduring the display update period 502 and the current drawn during thelong H-blank interval 506 less than or equal to the threshold; (3) theequalizer 230 can determine the number of source drivers 212 and/or thenumber of current consumption circuits 234 to be activated that consumeI_(additional); and (4) the equalizer 230 can activate the selectedsource drivers 212 and/or current consumption circuits 234 to consumethe current I_(additional).

During the step 606, at step 714, the equalizer 230 can control secondcircuitry during the first time period to equalize power drawn from thepower supplies 224 during the first and second time periods within athreshold. In an embodiment, the second circuitry comprises the sensecircuitry 204. Thus, at step 716, the equalizer 230 can reduce thecurrent consumed by the sensor circuitry 204 during the second timeperiod.

In an embodiment, the equalizer 230 can perform the following algorithmduring step 714: (1) the equalizer 230 can determine a thresholdrepresenting a target difference between the current drawn during thedisplay update period 502 and the current and the current drawn duringthe long H-blank interval 506; (2) the equalizer 230 can determine acurrent I_(reduction) that makes the difference between the currentdrawn during the display update period 502 and the current drawn duringthe long H-blank period 506 less than or equal to the threshold; (3) theequalizer 230 can determine an operating voltage for the sensorcircuitry 204 to consume (I_(sense)−I_(reduction)); and (4) theequalizer 230 can control the sensor circuitry 204 consume the current(I_(sense)−I_(reduction)).

In an embodiment, the equalizer 230 can perform a combination of steps716 and steps 710 and/or 712.

The embodiments and examples set forth herein were presented in order tobest explain the embodiments in accordance with the present technologyand its particular application and to thereby enable those skilled inthe art to make and use the invention. However, those skilled in the artwill recognize that the foregoing description and examples have beenpresented for the purposes of illustration and example only. Thedescription as set forth is not intended to be exhaustive or to limitthe invention to the precise form disclosed.

In view of the foregoing, the scope of the present disclosure isdetermined by the claims that follow.

We claim:
 1. A method of performing capacitive sensing and displayupdating in an integrated capacitive sensing device and display device,the method comprising: driving a plurality of display electrodes withone or more display voltages from one or more supplies during a firsttime period, the one or more voltages configured to drive the displaypixels; initiating a long horizontal blanking interval during a secondtime period; driving a plurality of sensor electrodes with one or moresensing voltages from the one or more supplies during the second timeperiod to perform capacitive sensing; and activating first circuitryduring one of the first time period or the second time period to drawcurrent to equalize power drawn from the one or more supplies during thefirst and second time periods within a threshold.
 2. The method of claim1, wherein the power drawn from the one or more supplies is higherduring the first time period than during the second time period, andwherein the first circuitry is activated during the second time period.3. The method of claim 1, wherein the power drawn from the one or moresupplies is higher during the second time period than during the firsttime period, and wherein the first circuitry is activated during thefirst time period.
 4. The method of claim 1, wherein activating thefirst circuitry comprises driving one or more source drivers during thesecond time period while the one or more source drivers are disconnectedfrom the display device.
 5. The method of claim 1, wherein activatingthe first circuitry comprises driving one or more current consumptioncircuits during either the first time period or the second time period.6. The method of claim 1, further comprising: controlling secondcircuitry during the other of the first time period or the second timeperiod to further equalize power drawn from the one or more suppliesduring the first and second time periods within the threshold.
 7. Themethod of claim 6, wherein controlling the second circuitry comprisesreducing current consumed by one or more source drivers during the firsttime period while the one or more source drivers are coupled to thedisplay device.
 8. A processing system for a capacitive sensing deviceand a display device, comprising: source drivers configured to drive aplurality of display electrodes with one or more display voltages fromone or more supplies to drive display pixels of the display deviceduring a first time period; sensing circuitry configured to drive aplurality of sensor electrodes with one or more sensing voltages fromthe one or more supplies during a second time period to performcapacitive sensing; a controller configured to initiate a longhorizontal blanking interval during the second time period; and anequalizer configured to activate first circuitry during one of the firsttime period or the second time period to draw current to equalize powerdrawn from the one or more supplies during the first and second timeperiods within a threshold.
 9. The processing system of claim 8, whereinthe power drawn from the one or more supplies is higher during the firsttime period than during the second time period, and wherein theequalizer is configured to activate the first circuitry during thesecond time period.
 10. The processing system of claim 8, wherein thepower drawn from the one or more supplies is higher during the secondtime period than during the first time period, and wherein the equalizeris configured to activate the first circuitry during the first timeperiod.
 11. The processing system of claim 8, wherein the equalizer isconfigured to activate the first circuitry by driving one or more sourcedrivers during the second time period while the one or more sourcedrivers are disconnected from the display device.
 12. The processingsystem of claim 8, wherein the equalizer is configured to activate thefirst circuitry by driving one or more current consumption circuitsduring either the first time period or the second time period.
 13. Theprocessing system of claim 8, wherein the equalizer is furtherconfigured to: control second circuitry during the other of the firsttime period or the second time period to further equalize power drawnfrom the one or more supplies during the first and second time periodswithin the threshold.
 14. The processing system of claim 13, wherein theequalizer is configured to control the second circuitry by reducingcurrent consumed by one or more source drivers during the first timeperiod while the one or more source drivers are coupled to the displaydevice.
 15. The processing system of claim 8, wherein the equalizercomprises an equalizer circuit coupled to the first circuitry.
 16. Aninput device comprising a capacitive sensing device and a displaydevice, the input device comprising: a plurality of sensor electrodes; aplurality of display electrodes; and a processing system, coupled to theplurality of sensor electrodes and the plurality of display electrodes,the processing system including: source drivers configured to drive theplurality of display electrodes with one or more voltages from one ormore supplies to drive display pixels of the display device during afirst time period; sensing circuitry configured to drive the pluralityof sensor electrodes with one or more sensing voltages from the one ormore supplies during a second time period to perform capacitive sensing;a controller configured to initiate a long horizontal blanking intervalduring the second time period; and an equalizer configured to activatefirst circuitry during one of the first time period or the second timeperiod to draw current to equalize power drawn from the one or moresupplies during the first and second time periods within a threshold.17. The input device of claim 16, wherein the power drawn from the oneor more supplies is higher during the first time period than during thesecond time period, and wherein the equalizer is configured to activatethe first circuitry during the second time period.
 18. The input deviceof claim 16, wherein the power drawn from the one or more supplies ishigher during the second time period than during the first time period,and wherein the equalizer is configured to activate the first circuitryduring the first time period.
 19. The input device of claim 16, whereinthe equalizer is configured to activate the first circuitry by drivingone or more source drivers during the second time period while the oneor more source drivers are disconnected from the display device.
 20. Theinput device of claim 16, wherein the equalizer is configured toactivate the first circuitry by driving one or more current consumptioncircuits during either the first time period or the second time period.